The answer is b. Fifth Amendment. It is also known as “Pleading the Fifth”. It is used for citing the freedom that allows a witness to refuse to answer questions where the answers might implicate him or her to avoid suffering a penalty for declaring the benefit. A defendant cannot be forced to become a witness at his or her own trial. But he or she decides to testify, he or she is not eligible to the privilege, and in conclusion can be drawn for refusing to answer a question while being cross-examined in court.